Any method you choose will be dependent on the terminal you're using. The Perl Cookbook, Recipe 4.18, "words program" offers a simplistic scrap of code for Linux. It would not work on Windows. It asks for extended information on the given filehandle, which the terminal program itself generally provides.

# not portable -- linux only
sub getwinsize {
    my $winsize = "\0" x 8;
    my $TIOCGWINSZ = 0x40087468;
    if (ioctl(STDOUT, $TIOCGWINSZ, $winsize)) {
        ($rows, $cols, $xpixel, $ypixel) = unpack('S4', $winsize);
    } else {
        $cols = 80;
    }
}
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You might do some research into termcap, which is the usual way of figuring out terminal capabilities and escape code sequences supported on a given Unix-style terminal. There are some CPAN modules which interface with the termcap facility.